Spark plug



1942- E. B. NOWOSIELSKI SPARK PLUG Filed May 1 Patented Nov. 10, 1942'SPARK PLUG Edward B. Nowosielski, Bloomfield, N. J., assignor,

by mesne assignments, to Bendix Aviation Corporation, South Bend, Ind.,a corporation of Delaware Application May 1, 1930, Serial No. 449,039

15 Claims.

This invention relates to ignition systems for internal combustionengines and more particularly to spark plugs.

One of the objects of the present invention is to provide an improvedspark plug which is both mechanically and electrically strong, and iscapable of long service without mechanical or electrical faults.

Another object is to provide an improved spark plug which embodies novelmeans for preventing the escape of gases from the engine cylinderthrough the spark plug structure with a consequent loss of compression.

A further object is to provide a spark plug of improved structure whichembodies novel electrical shielding means for preventing interferencewith the operation of sensitive electrical apparatus, such as radioequipment.

A still further object is to provide a spark plug embodying a novelgas-tight seal and an improved shielding means which on account of itssimplicity and small number of parts is rugged in structure, cheap tomanufacture and easy to assemble.

Several embodiments of the present invention are illustrated in theaccompanying drawing, but it is to be expressly understood that saiddrawing is for th purposes of illustration only and are not to beconstrued as a definition of the limits of the invention, referencebeing had for this purpose to the appended claims.

In the drawing:

Fig. 1 is a side elevation, partly in section, of one embodiment of thepresent invention;

I Fig. 2 is a front elevation of the embodiment shown in Fig. 1;

Figs. 3 and 5 are side elevations, partly in section, of otherembodiments of the present invention; and

Figs. 4 and 6 are sections taken on lines 44 and 6-6 of Figs. 3 and 5respectively.

Referring now to the drawing, wherein like reference characters indicatelike parts throughout the several views, Figs. 1 and 2 illustrate animproved spark plug which embodies novel means for forming a gas-tightseal to prevent the escape of gases through the body of the spark plugfrom the engine cylinder, and a novel form of electrical shield forpreventing interference with other sensitive electrical apparatus. Inthe form shown, said plug comprises, in general, a body portion, apositive electrode and a negative electrode. Body portion 1 isexteriorly threaded as at 8 for threaded engagement with an opening in acylinder wall of an internal combustion engine in the usual manner. Theupper part of body portion 1 -is internally threaded as at 9 and is oflarger diameter than the lower part so as to provide an inner shoulderIII.

The positive electrode comprises a metallic spindle II having at itslower end an enlarged head I2, which carries a spark gap point I3. Aninsulator I4, preferably a mica sleeve, surrounds electrode IIpractically throughout its length, resting at its lower end on head I2.A plurality of insulating washers I5, preferably of mica, surround thelower portion of electrode II and insulating sleeve I4 adjacent head I2,said washers also resting upon head I2 and preferably being ofincreasing outer diameters away from said head. On top of insulatingwashers I5 there is seated a gland I 6 externally threaded as at H andsurrounding the intermediate portion of electrode II and insulatingsleeve I4, but separated therefrom so as to provide a space for theinsertion of packing material. Gland I6 is provided with an inclinedbottom portion I8, the outer surface of which conforms in slope toshoulder III of body portion I, and with an annular groove I9 formed inits inner surface for purposes later to be described.

In the space thus formed between insulating sleeve I4 and gland I6.there is provided a sleeve 20 of compressible packing material,preferably copper. This sleeve 20 cf compressible material is forcedbetween insulating sleeve I4 and gland I6 under great pressure by anysuitable means so that groove I9 of gland I6 is completely filled withsaid material, and insulating SleeVS I4 is wedged into close engagementwith electrode II thus forming a double gas-tight seal around theelectrode.

A plurality of other insulating washers 2| are provided resting on topof gland I 6 and surrounding the remaining upper pcrtion of electrode IIand insulating sleeve I4, said washers preferably decreasing in diametertoward the top of electrode I l. Retaining head 22 is then placed aroundthe top of electrode II and rests upon washers 2|. Retaining head 22 isprovided with a countersunk bore 23 into which the top of electrode I Iis expanded by upsetting or any other suitable method, thus tightlyclamping together on said electrode, between retaining head 22 andbottom head I2, the assembly comprising washers 2|, gland I6, sleeve 20,and washers I5.

Suitable means are provided for attaching a cable or lead to electrodeII which, in the form shown, comprise a terminal member 24 fitted with asplit spring tip or terminal post 25. Terminal member 24 is placed overand in contact with electrode II and retaining head 22, and is securedthereto by a spun-over flange 26 which engages a corresponding collar 21formed on retaining head 22. V

The negative electrode of the spark plug preferably comprises asubstantially cupped-shape metallic thimble 28 having in its bottom aplurality of perforations 29 through one of which extends point l3 ofthe positive electrode II. Electrode 28 has its rim bent outwardly so asto form a flange 30 for the purpose of engaging shoulder I9 formed inbody portion I, when the spark plug is assembled.

In assembling the spark plug, the negative electrode 28 is placed inbody portion I, flange 30 resting on shoulder ID. The positive electrodeassembly as described above, is then threaded into body portion 1, theinclined bottom portion I8 of gland I6 tightly clamping flange 39 ofelectrode 29 between it and shoulder ID to form a gas-tight joint atthis point. If desired, flange 39 may be doubled upon itself so as toafford an extra thickness of metal at this point, thereby insuring thegas-tight integrity of the joint, and rendering it unnecessary to employthe usual gasket.

A lead or wire 3| is connected to the terminal post 25 in any suitablemanner, and, as shown, is provided with a terminal ring 32 which isadapted to slip over the split terminal 25. Lead 3| is covered withsuitable insulation 33 including a, metal shield 34 which may be formedof woven wire, for example.

In addition to the gas sealing means embodied in this spark plug, thereare also provided novel means for electrically shielding said plug so asto prevent interference with sensitive electrical apparatus such asradio equipment. In the form shown in Figs. 1 and 2, said shieldingmeans comprises a two-piece L-shaped metallic casing, and means withinthe casing for insulating it from the positive electrode l I and the endof lead 3I.

A lower casing member 35 surrounds the electrode I I approximatelythroughout its length and is secured to body portion I of the spark plugby means of an inwardly directed flange 36 which engages a circularshoulder 31 formed on body portion 1. Casing member 35 is substantiallycylindrical in shape except at its upper end where there is provided alaterally extending portion 38 of substantially semi-circular crosssection which surrounds the lower half of lead 3I.

A cap 39 is provided which cooperates with easing member 35 and closesthe top of electrode II and lead 3|. Cap 39 is also approximatelysemicircular in cross section and is provided with flanges 40 whichengage similar flanges 4| formed on casing member 35.

Means are provided for holding cap 39 in cooperative engagement withmember 35, and, in the form shown, comprise a bail 42, pivoted in member35 as at 43, the top of which engages a groove 44 formed in cap 39.

Suitable insulating means are provided within the above describedcasing, comprising, in the form shown, an upper insulator member 45,formed of porcelain or other suitable material, which is held within cap39 and which conforms to the shape of the top ofthe electrode II andlead 3I, and a lower insulator member 46 of the same material securedwithin casing member 35 and complementary to upper member 45. Insulatormember 46 also includes a vertical portion 41 which surrounds thepositive electrode assembly and rests upon the top of gland I6. It willbe understood that the two parts of the shielding casing may be die-castaround the insulator members, electro-deposited thereon, or formed inany other suitable manner.

In Figs. 3 and 4, there is illustrated another embodiment of the presentinvention. In this form, the packing material placed between theinsulating sleeve I4 and gland I6 comprises a pair of wedge rings 48 and49 of compressible material such as copper. These rings are placedbetween sleeve I4 and gland I6 with their inclined faces in engagementand with the base of ring 48 resting on the inclined bottom portion I8of gland I6. Pressure is then applied, by any suitable means, to the topof ring 49, and the resultant expansion of the rings forms a doublegas-tight seal around electrode II in a similar manner as described forsleeve 20.

The shielding casing shown in Figs. 3 and 4 diners from that of Figs. 1and 2 in that it is divided in a vertical plane into two symmetricalhalves 50 and 5|, which are held together in cooperative relation bymeans of a clamp ring 52 having a screw 53. Clamp ring 52 is preventedfrom sliding ed the casing when in its clamped position by means of anannular projection 54 formed on said casing. In this embodiment,engagement with body portion I of the spark plug is obtained by theclamping action between a flange 55 formed at the lower end of theshielding casing, and the upper circular portion of body 1.

Figs. 5 and 6 show an additional form of shielding casing, which issimilar to that of Figs. 3 and 4 in that the casing is dividedin avertical plane into two symmetrical halves 56 and 51. These halves,however, are hinged together as at 53, and are connected to body portionI of the spark plug by means of a sleeve or ring 59 which engagesshoulder 3'l, the casing telescoping within said ring and being securedthereto as by screws 60.

There is thus provided an improved spark plug structure which is ruggedand strong both mechanically and electrically, and which is compactlyand easily assembled from a small number of parts. Due to its simplicityit is also cheap to manufacture. Novel means are provided in this sparkplug for efiectively preventing the escape of gases from the enginecylinder, through the spark plug structure, and thus decreasing less ofcompression. Also, novel shielding means are provided which totallyinsulate and electrically shield all portions of the spark plug which byradiation of the high tension ignition current might cause interferencewith sensitive electrical apparatus in the vicinity, such as radioequipment. The novel shielding means are also simple in structure, andmay be quickly and easily attached to or detached from the spark plugbody.

It will be obvious that the invention is not limited to the specificforms described and illustrated in the drawing, but is capable of avariety of mechanical embodiments. Various changes, which will nowappear to those skilled in the art, may be made in the form, details ofconstruction and arrangement of parts without departing from the spiritof the invention, and it will be understood that the shielding means maybe employed with spark plug structures other than that illustrated.Reference is therefore to be had to the appended claims for a definitionof the limits of the invention.

What is claimed is:

1. Apparatus of the class described comprising in combination a sparkplug body, a portion in-' cluding an electrode extending therefrom, acable connected to said electrode, means for housing and shielding saidelectrode and cable comprising an L-shaped metallic casing havinginsulating means therein, said means in one arm of said casing beingshaped to receive said cable and in the other arm to cover the extendedportion of said spark plug, said casing being formed in two parts whichregister, one with the other, along a plane passing through thelongitudinal axis of said cable, and means for connecting said partstogether.

2. Apparatus of the character described, comprising in combination, aspark plug body having a circular shoulder, an electrode extendingtherefrom, a cable connected to said electrode, means for shielding andhousing said electrode and cable comprising a two-piece metallic elbowinto one arm of which said cable extends, the other arm surrounding saidelectrode, means for insulating said elbow from said electrode andcable, means for holding the two said pieces of said elbow incooperative relation along a plane passing through the longitudinal axisof said cable, and separate means for securing said elbow to saidcircular shoulder of the spark plug body.

3. Apparatus of the class described comprising in combination a sparkplug body having a circular shoulder, an electrode extending therefrom,a cable connected to said electrode,'a metallic casing having engagementwith said circular shoulder and extending substantially the length ofsaid electrode, a metallic cap cooperating with the outer extremity ofsaid casing to enclose and shield said electrode and cable, meansincluding a bail for securing said cap to said casing, and means forinsulating said casing and cap from said electrode and cable.

4. Apparatus of the character described, comprising, in combination witha spark plug body and an electrode extending therefrom, a cableconnected to said electrode, means for shielding and housing saidelectrode and cable comprising a two-piece metallic elbow into one armof which said cable extends, the other arm surrounding said electrode,means including a two-piece insulator for insulating said elbow fromsaid electrode and cable, and means for holding the two pieces of saidelbow in cooperative relation along a plane passing through thelongitudinal axis of said cable.

5. A shield for a spark plug and its associated cable comprising ametallic elbow constituted by a pair of sections enclosing the plug andcable, said sections being in registry along a plane passing through thelongitudinal axis of the cable, and pivotally mounted means for holdingsaid sections in registry along said plane.

6. A shield for a spark plug and its associated cable comprising ametallic elbow constituted by a pair of sections enclosing the plug andcable, said sections being in registry along a plane passing through thelongitudinal axis of the cable, and means for holding said sections inregistry along said plane, said means including a clamping deviceengaging both said sections.

7. A shield for a spark plug and its associated cable comprising ametallic elbow constituted by a pair of sections enclosing the plug andcable, said sections being in registry along a plane passing through thelongitudinal axis of the cable, and pivotally mounted means for holdingsaid sections in registry along said plane, said means ,including aclamping device engaging both said sections and having its ends securedin one only of said sections.

8. In an engine ignition system, a shielded cable and a tubular sparkplug shell, a metallic housing connecting the cable shield and tubularshell, said housing including a body of insulating material and upperand lower metalcoverings joined together along mating edges andenclosing said body, in such manner that opposite ends of the lowercovering have conducting relationship to the cable shield and the sparkplug shell respectively; said body of insulating material having a borein line with said tubular spark plug shell, and means extending throughsaid bore and into said tubular shell for supplying current to the sparkgap region of the plug.

9. In combination with a spark plug having a body portion provided witha shoulder, a metallic member surrounding said plug and having a portion extending inwardly for engagement with said shoulder, a secondmetallic member having edge engagement with the edge of the first, andmeans engageable with the upper most surface of said second metallicmember for securing said second metallic member in operativerelationship to the first.

10. In combination with an enginecylinder, a spark plug insertable intosaid cylinder, a spark plug shield comprising a metallic cup having aportion in engagement with both the plug and the cylinder, a dielectricbody extending into said cup, and a metallic cap extending over only theuppermost surface of said dielectric body and secured to said cup withtheir edges in register.

11. In combination with a spark plug and a radio shielded cabletherefor, shielding means for the plug comprising a lower shieldingmember extending upwardly to a point beyond the upper end of the plug,an upper shielding member detachably connected to said lower member, andan insulating member within said shielding means, said insulating memberhaving a skirt extending around the upper portion of the plug.

12. A spark plug shield of the type including a. plurality of shieldingparts for enclosing the plug and a dielectric body disposed between theplug and shielding parts, said dielectric body having a tubular passagefor the introduction of the ignition cable, characterized by the factthat two of said shielding parts separate substantially along a planethrough the longitudinal axis of said passage, and a clamp surroundssaid parts for retaining the said parts in operative position.

13. A spark plug shield of the type including a plurality of shieldingparts for enclosing the plug and a dielectric body disposed between theplug and shielding parts, said dielectric body having a tubular passagefor the introduction of the ignition cable, characterized by the factthat two of said shielding parts separate substantially along a planethrough the longitudinal axis of said passage.

14. In combination with a shielded conductor and a spark plug includinga metal shell having a wrench receiving portion and a shoulder belowsaid wrench receiving portion, a device for preventing radiation ofelectrical energy therefrom comprising a casing formed of complementarysections, one of which has an apertured portion for engagement with saidshoulder and a portion of wider bore surrounding but spaced from saidwrench receiving portion, means adapted to hold said sections in contactwith each other along a plane passing through said posed between saidcasing and said plug.

15. In combination with a shielded conductor and a spark plug includinga metal shell having a wrench receiving portion and a shoulder belowsaid wrench receiving portion, a device for preventing radiation ofelectrical energy therefrom comprising a casing formed of complementarysections, one of which has an apertured portion for engagement with saidshoulder and a portion of wider bore surrounding but spaced each otheradjacent said conductor, and a (11-.

electric body confined lay said casing sections. EDWARD B. NOWOSIELSKI.

